Over the past decade, mapping studies in human atrial fibrillation (AF) have found that atrial electrograms during sustained atrial fibrillation have three distinct patterns: single potential, double potential and complex fractionated atrial electrograms (CFAE). Areas of CFAE tend to be atrial fibrillation substrate sites and become important target sites for treatment, typically by ablation of endocardial tissue. For this reason, some practitioners now treat left atrial fibrillation not only by the accepted practice of ablating tissue around the ostia of the pulmonary veins (known as pulmonary vein isolation, or PVI), but also by ablating areas having persistent CFAEs.
U.S. Patent Application Publication 2007/0197929, whose disclosure is incorporated herein by reference, describes automatic detection and mapping of CFAEs within cardiac chambers. Electrogram signals are analyzed to count the number of complexes whose amplitude and peak-to-peak intervals meet certain criteria. Functional maps indicating average complex interval, shortest complex interval, and confidence levels are produced for display.
Kong et al. describe a meta-analysis of six randomized controlled trials to compare PVI alone with PVI plus CFAE ablation, in “Efficacy of Adjunctive Ablation of Complex Fractionated Atrial Electrograms and Pulmonary Vein Isolation for the Treatment of Atrial Fibrillation: A Meta-Analysis of Randomized Controlled Trials,” Europace (2010), which is incorporated herein by reference. The authors found PVI followed by adjunctive CFAE ablation to be associated with increased freedom from AF after a single procedure. On the other hand, adjunctive CFAE ablation increased procedural, fluoroscopy, and radio frequency (RF) application times. The authors concluded that the risk/benefit profile of adjunctive CFAE ablation deserves additional study and longer-term follow-up.
When a catheter is inserted into a chamber of the heart and brought into contact with the inner heart wall, it is generally important that the distal tip of the catheter engage the endocardium with sufficient pressure to ensure good contact. Excessive pressure, however, may cause undesired damage to the heart tissue and even perforation of the heart wall. A number of patent publications describe catheters with integrated pressure sensors for sensing tissue contact. For example, U.S. Patent Application Publications 2009/0093806 and 2009/0138007, whose disclosures are incorporated herein by reference, describe catheters with this sort of pressure sensing.